This invention relates to novel piperidine derivatives of formula (I) and a process for the preparation thereof. 
wherein
R1 is H or C1-C6alkyl wherein the C1-C6alkyl moiety is straight or branched;
R2 is xe2x80x94COOH or xe2x80x94COOalkyl wherein the alkyl moiety has from 1 to 6 carbon atoms and is straight or branched; or
stereoisomers or pharmaceutically acceptable acid addition salt thereof.
Terfenadine, xcex1-[4-(1,1-dimethylethyl)phenyl]-4-(hydroxydiphenylmethyl)-1-piperidinebutanol, is a known antihistaminic agent which is currently available commercially under the name Seldane(copyright) with a recommended dosage of 60 mg b.i.d. (See PHYSICIAN""S DESK REFERENCE, 52nd Edition, 1998, pp. 1238-1244, Medical Economics Data, a division of Medical Economics Company, Inc. Montvale, N.J.). Terfenadine is disclosed in U.S. Pat. No. 3,878,217, issued Apr. 15, 1975. Sorken and Heel have provided a review of the pharmacodynamic properties and therapeutic efficacy of terfenadine [Drugs 29, 34-56 (1985)].
Terfenadine undergoes extensive (99%) first pass metabolism to two primary metabolites (fexofenadine) and an inactive dealkylated metabolite. Fexofenadine, a.k.a. 4-[1-hydroxy-4-[4-(hydroxydiphenyilmethyl)-1-piperidinyl]butyl-xcex1,xcex1-dimethyl-benzeneacetic acid, has been disclosed as an antihistaminic agent having oral activity in U.S. Pat. No. 4,254,129, issued Mar. 3, 1981. It is currently available commercially under the name Allegra(copyright) (See PHYSICIAN""S DESK REFERENCE, 52nd Edition, 1998, pp. 1189-1190, Medical Economics Data, a division of Medical Economics Company, Inc. Montvale, N.J.).
An object of the present invention is to provide novel piperidine derivatives of formula (I) useful for the treatment of allergic disorders. It is a further object to provide a process for the preparation of said derivatives and to provide novel intermediates useful for preparation of the same.
Additionally, it is an object of the present invention to provide a method of treating a patient suffering from an allergic disorder comprising administering to said 10 patient an effective antiallergic amount of a compound of formula (I).
Furthermore, it is an object of the present invention to provide a composition comprising an assayable amount of a compound of formula (I) in admixture or otherwise in association with one or more pharmaceutically acceptable carriers or excipients.
Another object of the present invention is to provide novel processes for the preparation of intermediates useful for the synthesis of fexofenadine and related compounds.
Upon further study of the specification and appended claims, further objects and advantages of this invention will become apparent to those skilled in the art.